diff --git a/autotest/test_cli.py b/autotest/test_cli.py
new file mode 100644
index 00000000..82361089
--- /dev/null
+++ b/autotest/test_cli.py
@@ -0,0 +1,55 @@
+from types import SimpleNamespace
+
+import pytest
+
+from modflow_devtools import cli
+
+
+class _Registry:
+    def __init__(self, release_id, cache_path, error=None):
+        self.release_id = release_id
+        self.cache_path = cache_path
+        self._error = error
+
+    def sync(self):
+        if self._error:
+            raise self._error
+
+
+class _ModelConfig:
+    def __init__(self, failed):
+        self._failed = failed
+
+    def sync(self):
+        return {"src": SimpleNamespace(failed=self._failed)}
+
+
+@pytest.fixture
+def fake_registries(monkeypatch, tmp_path):
+    def _fake(dfn_error=None, model_failed=()):
+        from modflow_devtools.dfns.registry import RemoteDfnRegistry
+        from modflow_devtools.models import ModelSourceConfig
+
+        registry = _Registry("owner/repo@1.0", tmp_path, dfn_error)
+        monkeypatch.setattr(RemoteDfnRegistry, "load_default", lambda: {"r": registry})
+        monkeypatch.setattr(ModelSourceConfig, "load", lambda: _ModelConfig(list(model_failed)))
+
+    return _fake
+
+
+def test_sync_all_succeeds(fake_registries, capsys):
+    fake_registries()
+    assert cli._sync_all() == 0
+    assert "All registries synced!" in capsys.readouterr().out
+
+
+def test_sync_all_fails_on_dfn_error(fake_registries, capsys):
+    fake_registries(dfn_error=OSError("no network"))
+    assert cli._sync_all() == 1
+    assert "Failed to sync owner/repo@1.0: no network" in capsys.readouterr().out
+
+
+def test_sync_all_fails_on_model_error(fake_registries, capsys):
+    fake_registries(model_failed=[("current", "models.toml not found")])
+    assert cli._sync_all() == 1
+    assert "Models synced successfully" not in capsys.readouterr().out
diff --git a/modflow_devtools/cli.py b/modflow_devtools/cli.py
index c80e1e19..b5c4d949 100644
--- a/modflow_devtools/cli.py
+++ b/modflow_devtools/cli.py
@@ -21,24 +21,32 @@
 import sys
 
 
-def _sync_all():
+def _sync_all() -> int:
     """Sync all registries (dfns, models). The Programs API has no registry to sync -
-    it installs directly from GitHub releases and tracks installs in a local ledger."""
+    it installs directly from GitHub releases and tracks installs in a local ledger.
+    Returns 0 if everything synced, 1 if anything failed."""
     print("Syncing all registries...")
     print()
+    failed = False
 
     # Sync DFNs
     print("=== DFNs ===")
     try:
-        from modflow_devtools.dfns.registry import sync_dfns
-
-        registries = sync_dfns()
-        for registry in registries:
-            meta = registry.registry_meta
-            print(f"  {registry.ref}: {len(meta.files)} files")
+        from modflow_devtools.dfns.registry import RemoteDfnRegistry
+
+        registries = RemoteDfnRegistry.load_default()
+        for registry in registries.values():
+            try:
+                registry.sync()
+                n_files = len(list(registry.cache_path.glob("*.*")))
+                print(f"  {registry.release_id}: {n_files} files")
+            except Exception as e:
+                print(f"  [-] Failed to sync {registry.release_id}: {e}")
+                failed = True
         print(f"Synced {len(registries)} DFN registry(ies)")
     except Exception as e:
         print(f"Error syncing DFNs: {e}")
+        failed = True
     print()
 
     # Sync Models
@@ -47,13 +55,21 @@ def _sync_all():
         from modflow_devtools.models import ModelSourceConfig
 
         config = ModelSourceConfig.load()
-        config.sync()
-        print("Models synced successfully")
+        results = config.sync()
+        if any(result.failed for result in results.values()):
+            failed = True
+        else:
+            print("Models synced successfully")
     except Exception as e:
         print(f"Error syncing models: {e}")
+        failed = True
     print()
 
+    if failed:
+        print("Some registries failed to sync.")
+        return 1
     print("All registries synced!")
+    return 0
 
 
 def main():
@@ -85,7 +101,7 @@ def main():
 
     # Dispatch to the appropriate module CLI with remaining args
     if args.subcommand == "sync":
-        _sync_all()
+        sys.exit(_sync_all())
     elif args.subcommand == "dfns":
         from modflow_devtools.dfns.__main__ import main as dfns_main